An agrometeorological-spectral model to estimate soybean yield, applied to southern Brazil

Soybean yield is modelled from data gathered from crops in Rio Grande do Sul State, Brazil. The model comprises an agrometeorological term, obtained by adjusting the multiplicative model of Jensen, modified by Berlato, and a spectral term, obtained from National Oceanic and Atmospheric Administration (NOAA) satellite images of the maximum Normalized Difference Vegetation Index (NDVI). The weather data used to calculate the relative evapotranspiration (ET r /ET 0) cover the period from 1975 to 2000, and the NDVI/NOAA images were obtained from 1982 to 2000. Application of the agrometeorological-spectral model produced better yield estimates (of about 5%) than Jensen's model, allowing the further generation of yield maps for the most significant soybean production regions within the Rio Grande do Sul State.